The invention relates generally to vehicle tires and rims and more particularly to an integral tire and rim assembly wherein the tire and rim components are permanently secured to one another thereby forming a wheel and tire assembly from which the tire may not be dismounted.
A major result from the shift to smaller, energy efficient vehicles has been the change of drive trains from rear wheel drive to front wheel drive. The front wheel drive power train offers many advantages which are consonant with the goal of fuel efficiency such as a shortened and simplified power flow path and reduced power train component weight. Several other features of front wheel drive systems, both inherent and peripheral, such as transverse engine mounting, improved interior vehicle space, and simplified vehicle assembly are also harmonious with the contemporary goal of the energy efficient vehicle.
Examination of the front wheel drive power train reveals that not every aspect is synergistic, or even complementary, with other design constraints. The difficulties attendant providing the five functions of rotation, suspension, drive, steering, and braking provide a case in point. Such plural and diverse functions place a great premium on space in the region adjacent the wheels and no where is this more true than with regard to the braking mechanism which is typically disposed adjacent and preferably concentrically and axially within the wheel rim itself. A new generation of vehicle wheels having the spider disposed in substantially the same plane as the outboard wheel flange to accommodate the braking mechanism substantially within the wheel rim is common place.
One design consideration which has hampered further reductions in size and thus also weight is the necessity of including an inwardly directed well in the rim which receives the inextensible beads of a tire during installation and removal from the rim. Elimination of the well would provide additional volume within the wheel rim to accommodate brake and drive components.
Elimination of the well in the wheel rim is desirable from a second standpoint. As noted above, the tire beads and thus its inside diameter are substantially inextensible. The inclusion of the wheel rim well is thus mandated by the necessity of installing tires on the rim.
The prior art discloses wheel rims without wells as well as at least one method for assembling same. U.S. Pat. No. 3,639,964 discloses a well-less rim having one conventional flange and a smaller flange which is first deformed inwardly to a diameter no greater than the outside diameter of the rim. An annular flange having a cross section similar in cross section to the conventional flange is then placed onto the rim with the tire and the inwardly deformed, smaller flange is then rolled outwardly into position to maintain both the tire and the annular flange on the rim. Maintenance of proper tire bead to rim seal in this design appears to be problematic due to the circumferential gap between the annular flange and rim and air pressure within the tire which tends to force it radially away from the rim.
U.S. Pat. No. 4,121,643 discloses a rim which is fabricated with a pair of wells, one of which is filled with a resilient ring and the second of which is collapsed onto itself after the tire has been installed on the rim in a conventional manner. This configuration does not, of course, provide improved internal rim volume inasmuch as the wells are, in fact, present though in a modified form. It does, however, apparently provide improved run-flat performance.